Does the medicinal leech Hirudo medicinalis feel well in the Netherlands (Hirudinea)? This paper provides information on the medicinal leech Hirudo medicinalis Linnaeus, 1758 particularly in The Netherlands. Although this species was common in The Netherlands in the 18th century, nowadays it is very rare. Most animals were found in waters on sandy soil (71%): dune pools (10%) and pleistocene sandy areas (61%), where it inhabits especially soft water moor and heathland pools. About 20% of the records originate from river areas, where the species can be found in breakthrough ponds and oxbow lakes. Only 9% of the records are from fen and clay areas. Records of single specimens are not proof of an established population, because these specimens could also have survived after dispersal by waterfowl. Ten populations are currently known in The Netherlands. The leech is an indicator of special conditions such as high temperatures (shallow water), aerobic soil (e.g. sand for egg development) as well as of high biodiversity (feeding on snails, fish, amphibians, water birds and mammals). The medicinal leech is therefore threatened in The Netherlands by acidification, eutrophication and desiccation of their typical water biotopes causing an elimination of their vital prey (snails, fish and amphibians). Also the changed land use in agriculture is not favourable for the medicinal leech. In the past there were many drinking pools for cattle; nowadays drinking pools are very scarce and replaced by automated drinking systems. Management to restore the typical biotopes of the medicinal leech will further favour the presence of a lot of other species considered important to nature conservancy.